Sau đó beamforming với Moore-Penrose pseudoinverse 34,53-56 A + cung cấp cho các vector trọng lượng của sự chậm trễ cho tất cả các XR, XT τ hτ (XT, XR) = A + Tf (XT, XR) τ (3,36)nT e là vector coeffcients chuyển ở tần số 192-ban nhạc nghe. Điều này cho chúng ta coeffcients chuyển từ tất cả các vị trí XT để tất cả các vị trí XR một cách riêng biệt cho mỗi τi chậm trễ. | 21 Circular adaptive antenna array beam width 64 8 dB gain improvement over 25 nodes grid No PC Global PC 22 Ideal adaptive antenna 20 nodes no Protocol 23 nulling improvement over omni o omnidirectional case Packet transmission is D directional directional at sender receiver ORTS DCTS DRTS DCTS DRTS OCTS ORTS OCTS STDMA Six-element circular antenna array 10 fixed patterns no adaptation Omni 45 beamwidth 100 nodes 1500 m2 2-ray propagation model no nulling 400 kbps 225 nodes grid Local PC No PC Global PC Local PC PC power control Beamwidth 20 nodes degree 90 60 30 10 35 57 100 142 64 107 143 186 28 43 n a 57 29 50 86 121 n a 400 n a 400 No mobility RX directional DVCS DVCS-Ideal TX omnidirectional TX RX directional 800 kbps Mbps Mbps ADAPTIVE MAC FOR WLAN WITH ADAPTIVE ANTENNAS 155 156 ADAPTIVE MEDIUM ACCESS CONTROL Figure False beamforming. Reproduced by permission of IEEE 27 . optimization is a single-entry cache scheme wh ich works as follows If a node beamforms incorrectly in a given tìmeslot it eemembers that direction in a single-entry cache. In the next slot if the maximum signal strengt l again in the direction recorded in the single-entry cache then the node ignores that direction and beamforms towards the second strongest signal. If the node receives a packet correctly . it was the intended recipient it does not change the cache. If it receives a packet incorrectly it updates the cache with this new direction. Ifthere is nopacketin a slotfromthedirectionrecorded inthecache the cache is reset. The protocol is based on the lb standard. As in the case of the Smart-Alotapnotocel nransmittersbeamformtowrrdstheir heceinertand transmit a short sender- b K h ehath_wtnmim e . daeamiieoo don con immediately follow the tone with a packet. Instead it waits for a receiver-tone and only thenttant m its . After transmission of a packet it waits for the
